Is it true that older jurors are more likely to convict?

We’ve written about the older juror before and the benefits of having them on your jury (sometimes). When it comes to actual trial practice, Prosecutors are more likely to use their peremptories to strike the younger potential juror while Defense attorneys are more likely to use theirs to strike the older potential juror. So, is it true that the older juror is more conviction-prone? Sadly, it would seem so.

Researchers examined data from more than 700 felony trials in Florida’s Sarasota and Lake Counties from 2000-2010. They were able to collect data not only on seated jurors but also to gather the same data on the entire pool for comparison. The researchers found the voir dire pattern noted above (with Prosecutors striking the younger juror and Defense attorneys striking the older juror) but note that the protected categories of race and gender were not disproportionately struck. That is, prosecutors and defense attorneys were about equally likely to strike black versus white and female versus male potential jurors.

The researchers look at how the age composition of the jury pool (randomly selected to appear that particular day) is related to conviction rate. They found that the average age of the venire drawn for a case is highly correlated to the age of the seated jury. That is, when potential jurors are called for jury selection, if the average age is above 50 (which happens in about half the trials in these counties), the seated jury will also be older. If the average age of the jury pool is below 50, the seated jury will also be younger. Makes sense.

When the average age of the jury pool is greater than 50 years, there is a 79% conviction rate.

When the average age of the jury pool is less than 50 years, there is a conviction rate of only 68% (and yes, those differences are statistically significant).

In other words, the older juror is more likely to convict. Conviction rates, say the authors, rise 1% with each year of increase in the average age of a jury. Specifically, “if a male defendant, completely by chance faces a jury pool that has an average age above 50, he is [snip] more likely to be convicted than if he faces a jury pool with an average age less than 50”.

Obviously, the age of the jury has nothing at all to do with the evidence you present, the quality of your presentation, or the merits of the prosecution. It is a randomly occurring event which, in turn, can mean that an acquittal or conviction can also be a random event. The authors question if this represents a “fundamental lack of equity with respect to the quality of true nature of the evidence in a case”. They believe this random conviction increase provides an argument for increasing the number of jurors in Florida from the current 6 required (except for death penalty cases) to a higher number in order to reduce the random variations in outcome that are independent of the evidence admitted and presented.

And until that happens (or if it happens), it probably makes sense to keep using peremptories to attempt to either increase or decrease the age of your jury.

Anwar, S., Bayer, P., & Hjalmarsson, R. (2012). The role of age in jury selection and trial outcomes. National Bureau of Economic Research Working Paper. DOI: 10.2139/ssrn.2014963